Tumor vaccines are typically composed of tumor antigens and immunostimulatory molecules (e.g. cytokines or TLR ligands) that work together to induce antigen-specific cytotoxic T cells (CTLs) that recognize and lyse tumor cells. At this time, almost all vaccines contain either shared tumor antigens or whole tumor cell preparations (Gilboa, 1999). The shared tumor antigens are immunogenic proteins with selective expression in tumors across many individuals and are commonly delivered to patients as synthetic peptides or recombinant proteins (Boon et al., 2006). In contrast, whole tumor cell preparations are delivered to patients as autologous irradiated cells, cell lysates, cell fusions, heat-shock protein preparations or total mRNA (Parmiani et al., 2007). Since whole tumor cells are isolated from the autologous patient, the cells express patient-specific tumor antigens as well as shared tumor antigens. Finally, there is a third class of tumor antigens that has rarely been used in vaccines due to technical difficulties in identifying them (Sensi et al. 2006). This class consists of proteins with tumor-specific mutations that result in altered amino acid sequences. Such mutated proteins have the potential to: (a) uniquely mark a tumor (relative to non-tumor cells) for recognition and destruction by the immune system (Lennerz et al., 2005); (b) avoid central and sometimes peripheral T cell tolerance, and thus be recognized by more effective, high avidity T cells receptors (Gotter et al., 2004).
Thus a need exists for a method of identifying neoepitopes that are useful as tumor vaccines.